Peeling method and method for manufacturing display device using the peeling method

ABSTRACT

The present invention provides a simplifying method for a peeling process as well as peeling and transcribing to a large-size substrate uniformly. A feature of the present invention is to peel a first adhesive and to cure a second adhesive at the same time in a peeling process, thereby to simplify a manufacturing process. In addition, the present invention is to devise the timing of transcribing a peel-off layer in which up to an electrode of a semiconductor are formed to a predetermined substrate. In particular, a feature is that peeling is performed by using a pressure difference in the case that peeling is performed with a state in which plural semiconductor elements are formed on a large-size substrate.

TECHNICAL FIELD

The present invention relates to a peeling method of a functional thinfilm, specifically relates to a peeling method of a film or a layerhaving various elements. In addition, the present invention relates to atransferring method for pasting a peeled film to a film substrate, asemiconductor device and method for manufacturing thereof having a thinfilm transistor (hereinafter, referred to as a TFT) formed by using thetransferring method.

BACKGROUND ART

In recent years, attention has been paid to a technique of comprising aTFT by using a semiconductor thin film (thickness of around several toseveral hundreds nm) formed over a substrate having an insulatingsurface. A TFT is widely applied to an electronics device such as an ICor an electro-optical device, and is under development especially as aswitching element or a driver circuit of a display device.

Although a glass substrate or quartz substrate is often used in thedisplay device, it is easily broken and heavy, which are defects.Therefore, a glass substrate or quarts substrate is difficult to enlargein a mass production. Hence, forming a TFT element on a substrate withflexibility, typically, on a flexible plastic film is attempted.

However, when a high-performance polycrystalline silicon film is usedfor an active layer of a TFT, a high temperature process of severalhundred degrees Celsius is necessary in a manufacturing process; therebyit can not be directly formed on a plastic film.

Therefore, a method for peeling a peel-off layer existing on a substratethrough a separating layer from the substrate is proposed. For example,it is a method for providing a separating layer comprising amorphoussilicon, a semiconductor, nitride ceramics or organic polymer, then toradiate laser light through a substrate to generate a peeling in layerin the separating layer, followed by separating the substrate. (see thepatent document 1). Additionally, there is also a description that aliquid crystal display device is completed by pasting a peel-off layer(referred to as a layer to be transferred in the gazette) to a plasticfilm using the technique (see the patent document 2). In addition, whenarticles regarding a flexible display are looked, technologies of eachcompany are introduced. (see the non-patent document 1).

Patent Document 1

-   Unexamined Patent Publication No. 10-125929 gazette    Patent Document 2-   Unexamined Patent Publication No. 10-125930 gazette    Non-Patent Document 1-   Nikkei Microdevice, Nikkei BP, No. Jul. 1, 2002, Jul. 1, 2002, pages    71 to 72

DISCLOSURE OF INVENTION

However, there were a lot of problems in the aforementioned peelingprocess, and there was a room of improvement. In addition, it is neededto consider how to perform uniformly to a large-size substrate.

Therefore, the present invention provides a method for simplifying apeeling process as well as to conduct it easily. Additionally, thepresent invention provides a light emitting device, a crystal displaydevice, and other types of display devices formed by the aforementionedmethod.

In view of the aforementioned object, a feature of the present inventionis to simplify a manufacturing process by peeling a first adhesive andcuring a second adhesive in a peeling process at the same time. Inaddition, a feature of the present invention is to simplify amanufacturing process by devising the timing of transcribing a peel-offlayer to a predetermined substrate.

Moreover, it is preferable to cause a physical damage or to expose across-section of a peel-off layer in order to simplify peeling of thepeel-off layer.

In addition, when peeling in a condition that plural semiconductorelements are formed particularly on a large substrate, a feature is thata substrate is absorbed using difference in pressure and is peeled toraise precision and accuracy of peeling.

Specifically, as shown in FIG. 1 (A), a peel-off layer 101 is formed ona first substrate 100. A semiconductor element, an electrode,additionally, display function including a liquid crystal layer (aliquid crystal element) or a light emitting layer (a light emittingelement), a driving circuit and the like may be included in a peel-offlayer finally. A practitioner can determine a relation between peelingtiming and manufacturing state of a peel-off layer. For example, thepeel-off layer in FIG. 1 (A) may be a state in which a semiconductorelement and an electrode connected to the semiconductor element areformed, or a state in which a liquid crystal element or a light emittingelement are further formed.

The first substrate may have rigidity that can withstand followingpeeling process, and for example, a glass substrate, a quartz substrate,a ceramic substrate, a silicon substrate, a metal substrate or astainless steel substrate may be used.

Furthermore, a semiconductor element of a peel-off layer may be a TFThaving an amorphous semiconductor film, an organic TFT, a thin filmdiode, a photoelectric conversion element comprising a PIN junction ofsilicon, a silicon resistor element, a sensor element (typically apressure-sensitive finger print sensor using polycrystalline silicon),or the like. Additionally, if it is a TFT, it may be either a bottomgate type or a top gate type.

Then, as shown in FIG. 1 (B), a stress relaxation material 103 is formedon a peel-off layer. The stress relaxation material is not necessary ina peeling process, but it is preferable to provide in order to protectthe peel-off layer. A water-soluble resin, a thermosetting resin, aphoto-curing resin, or other resin may be used as a stress relaxationmaterial. In other words, an organic resin with high flexibility ispreferable in order to protect a peel-off layer, and moreover,considering removing it eventually, it also may be a material that isremoved physically, but a material in which adhesiveness decreases dueto water washing, heat or light is preferable.

Next, as shown in FIG. 1 (C), it is preferable to divide the firstsubstrate, the semiconductor element and the stress relaxation materialin order to simplify peeling of the peel-off layer. A laser, a cutter orthe like can be used as a dividing method.

It is preferable to expose a cross-section of a boundary face to beseparated in order to simplify peeling even though a cross-sectionprocess is not necessary in a peeling process. It may also be possibleto scratch on a cross-section surface of a boundary face to be separatedby a physical means such as a cutter. In addition, the peel-off layer orthe stress relaxation material may be cut in without separating thefirst substrate.

As shown in the FIG. 1 (D), a second substrate 105 is pasted on thepeel-off layer afterwards. At this time, although it is fixed by using afirst adhesive 106, when there is an adhesion function in a substrate initself, an adhesive is not necessary. It is preferable that a substratewith higher rigidity than that of the first substrate be used for thesecond substrate, and a quartz substrate may be utilized since it hascomparatively high rigidity. As the first adhesive, a peelable adhesive,for example, an ultraviolet peelable adhesive in which adhesiveness isweakened or which is peeled by an ultraviolet ray, a heat peelableadhesive in which adhesiveness is weakened or which is peeled by heat, awater-soluble adhesive or a two-sided tape in which adhesiveness isweakened or which is peeled by water washing, or the like may be used.

In addition, an auxiliary substrate 108 may be provided under the firstsubstrate to further assure a peeling process. An adhesive 107 is usedfor fix the substrate when the auxiliary substrate is not provided withadhesiveness. In addition, the identical adhesive may be used for fixthe second substrate and the auxiliary substrate, and the first adhesiveand the auxiliary substrate.

Then, as shown in the FIG. 1 (E), peeling is conducted by using aphysical means. When the auxiliary substrate is provided as shown inFIG. 1 (E), each of the second substrate and the auxiliary substrate maybe added with power working towards the reverse directions, and when theauxiliary substrate is not provided, it may be peeled by fixing a sheetwith high adhesiveness under the first substrate.

When it is a large-size substrate, in particular, the substrate may beabsorbed using difference in pressure to peel uniformly. In other words,for example, a substrate to be peeled is provided on a substrate inwhich a vacancy is formed, the vacancy is in the decompression or vacuumstate by a pump or the like, and a peeling may be conducted in the statethat the entire substrate to be peeled is fixed uniformly by differencein pressure.

Then as shown in FIG. 2 (F), a third substrate 110 is fixed under thepeeled layer. When the third substrate does not have adhesiveness initself, it is adhered through a second adhesive 111. As the thirdsubstrate, a substrate with a thin film thickness or a substrate withflexibility (flexible) (hereinafter referred to as a film substrate)such as a plastic substrate such as polycarbonate, polyarylate,polyethersulfone, a polytetrafluoroethylene substrate or a ceramicsubstrate may be used. As the second adhesive, an ultraviolet curableresin or a thermosetting resin can be used. However, the first adhesiveand the second adhesive need to have opposite features by an ultravioletray, heat or the like. In other words, adhesiveness of the firstsubstrate should be weakened or the substrate should be peeled and thesecond substrate should be cured due to an ultraviolet ray or heat. InFIG. 2 (F), adhesiveness of the first adhesive is weakened and thesecond adhesive is cured by being irradiating with an ultraviolet ray.In addition, an ultraviolet ray may be radiated both from top and bottomof the peeled layer or from one side of the peel-off layer. Then, asshown in FIG. 2 (G), the second substrate is peeled.

In this way, a peeling process can be simplified as peeling and fixingcan be conducted at the same time by the identical process such asradiating an ultraviolet ray or applying heat.

Then, as shown in FIG. 2 (H), the stress relaxation material is removedby being irradiated with an ultraviolet ray, heating or water washing.Moreover, it is preferable to perform plasma cleaning using an argon gasand an oxygen gas or bellclean cleaning to remove more precisely. Atthis time, as the stress relaxation material, a material which can beremoved in the same step of the first adhesive may be used. In otherwords, a material which can be removed by an ultraviolet ray is used asthe stress relaxation material, and peeling of the first adhesive,curing of the second adhesive, and removing of the stress relaxationmaterial can be performed simultaneously. Then, as shown in FIG. 2 (I),transferring of the peeled layer to the third substrate is completed.

A peeling process repeating the removal and curing of the adhesive fortransferring can be simplified by using the peeling methods. Therefore,in the peeling process of the present invention, it can be formed with apreferable yield since an entire peel-off layer can be peeled. Bypeeling an entire peel-off layer, plural semiconductor elements can beformed on one large-size substrate and a gang printing which cut thesubstrate every semiconductor device can be performed; thereby costreduction can be expected. In addition, the first substrate and the likecan be recycled; thereby a low cost display device can be achieved toutilize far more inexpensive film substrate.

As a result, a light emitting device, a liquid crystal display deviceand other display device having the TFT or the like are made thin, hardto damage even in being dropped and light-weight. In addition, displayon a curved surface or heteromorphic surface is made possible.

Peeling (including adhesiveness reduction) or curing of an adhesive canbe performed by the same process (ultraviolet ray irradiation andheating) according to the present invention. Consequently, amanufacturing process of a display device in addition to a peelingprocess can be simplified. Moreover, when plural display devices aremanufactured from a large-size substrate, besides the peeling process ofthe present invention, a process of peeling or transferring can beperformed accurately and simply by a pressure reduction device or thelike. In this way, the number of a manufacturing steps is reduced by thepeeling process of the present invention, and displays can be producedin large quantities with a preferable yield.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1E are drawings of explaining a peeling process of thepresent invention.

FIGS. 2F to 2I are drawings of explaining a peeling process of thepresent invention.

FIGS. 3A to 3I are drawings of manufacturing a light emitting deviceaccording to a peeling process of the present invention.

FIGS. 4A to 4E are drawings of manufacturing a light emitting deviceaccording to a peeling process of the present invention.

FIGS. 5A to 5F are drawings of manufacturing a liquid crystal displaydevice according to a peeling process of the present invention.

FIGS. 6A to 6D are drawings of manufacturing a liquid crystal displaydevice according to a peeling process of the present invention.

FIGS. 7A and 7B are drawings of explaining a gang printing using peelingprocess of the present invention.

FIGS. 8A to 8F are drawings of explaining an electronics device of thepresent invention.

FIG. 9 is a drawing of explaining an electronics device of the presentinvention.

FIGS. 10A and 10B are drawings of showing a cross-sectional TEMphotograph peeled according to the present invention.

FIGS. 11A and 11B are drawings of showing a cross-sectional TEMphotograph peeled according to the present invention.

FIGS. 12A to 121 are drawings of manufacturing a light emitting deviceaccording to a peeling process of the present invention.

FIGS. 13A to 13E are drawings of manufacturing a light emitting deviceaccording to a peeling process of the present invention.

FIGS. 14A to 14G are drawings of manufacturing a liquid crystal displaydevice according to a peeling process of the present invention.

FIGS. 15A to 15E are drawings of manufacturing a liquid crystal displaydevice according to a peeling process of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment modes of the present invention are described on the basis ofdrawings hereinafter. In addition, in all drawings for describing theembodiment mode, the same code is used in the same part or a part havingthe same function to omit the repetition of explanation.

Embodiment Mode 1

In the present embodiment mode, a peel-off layer is in a state in whichup to a light emitting element and a liquid crystal element are formed,and an example of a specific peeling process in the case of performingpeeling and transferring and of forming a top emission light emittingdevice according to the peeling process of the present invention isdescribed.

As shown in FIG. 3 (A), a metal film 201 is formed on a first substrate200. In the embodiment mode, a glass substrate with a film thickness ofapproximately 0.5 to 1.0 mm is utilized for the first substrate. As forthe metal film, a monolayer or a lamination layer comprising an alloymaterial or a compound material of W, Ti, Ta, Mo, Nd, Ni, Co, Zr, Zn,Ru, Rh, Pd, Os and Ir or containing the element as its main componentcan be used. Sputtering may be used as a manufacturing method for themetal film on the first substrate using metal as a target. In addition,a film thickness of the metal film is 10 nm to 200 nm, preferably 50 nmto 75 nm.

When an alloy of the abovementioned metal (for example, an alloy of Wand Mo: W_(x)Mo_(1-x)) is used as the metal film, it may be formed bysputtering after disposing plural targets such as first metal (W) andsecond metal (Mo), or an alloy target of first metal (W) and secondmetal (Mo). In this way, setting appropriately the way of forming themetal film can control the process for peeling and widen the margin ofthe process. For example, when a metal alloy is used, controlling thecomposition ratio of each metal in the alloys can control thetemperature of heat treatment and additionally, the necessity of heattreatment.

Afterwards, instead of a metal film, a nitrided metal film (metalnitride film) may be used. In addition, nitrogen or oxygen may be addedto the metal film. For example, ion implantation of nitrogen or oxygento the metal film may be performed, or the metal film may be formed bysputtering in a film formation chamber which shall be a nitrogen oroxygen atmosphere. Furthermore, nitride metal may be used as a target.

Afterwards, a semiconductor film is formed through a base film 207laminated over the metal film 201. In other words, an insulating filmrepresented by a base film may be provided between the metal film andthe semiconductor film in any number of layers of the insulating film.As the base film, a monolayer of an insulating film having silicon suchas a silicon oxide film, a silicon nitride film or a silicon oxynitridefilm, or lamination of these may be used. In the present embodimentmode, SiO₂ formed on the metal film with a thickness of 150 nm to 200 nmby sputtering, and SiON formed on the SiO₂ with a thickness of 80 to 100nm by a CVD method are provided. The base film prevents impuritydiffusion from a substrate or a metal film to a semiconductor film.

In addition, through the abovementioned process, an oxide film (a metaloxide film) 202 having the metal is formed on the surface of the metalfilm. The thickness of the metal oxide film may be 0.1 nm to 1 μm,preferably 0.1 nm to 100 nm, more preferably 0.1 nm to 5 nm. Inaddition, the oxidation film may be manufactured directly on the metalfilm.

Then, heat treatment is performed if necessary. By this heat treatment,the metal oxide film is crystallized, which causes a crystallinedistortion or a lattice defect (a point defect, a line defect, a planedefect (for example, a plane defect due to a crystallographic shearplane which is formed by gathered oxygen vacancies) or an expansiondefect). This is a state that the metal film is easily peeled.

Furthermore, by heating treatment, it is conceivable that a metal oxidehaving different crystal condition is formed by oxidation-reductionreaction due to diffusion of hydrogen contained in the semiconductorfilm. Therefore, it is a state that the metal film is easily peeled.

In addition, the abovementioned heat treatment can also serve as a heattreatment for crystallizing the semiconductor film. In other words, itis possible to form a crystalline semiconductor film and to crystallizea metal oxide film by heating a semiconductor film formed over a metalfilm.

After applying a metal element (represented by Ni element) whichpromotes crystallization, heat treatment may be performed, or a lasermay be radiated after the heat treatment to improve crystallinity of thesemiconductor film. In addition, in the case that a metal elementpromoting crystallinity is used, it is preferable to remove the metalelement by a gettering process or an etching process since it isunnecessary for a device.

Afterwards, the crystalline semiconductor film is patterned to have adesired shape, and a gate insulating film is formed using an oxide filmhaving silicon or a nitride film having silicon. A gate electrode isformed on the crystalline semiconductor film through the gate insulatingfilm, and an impurity region is formed using the gate electrode as amask. A laminated structure of W and TaN is used for the gate electrode,and source and drain regions, a low concentration impurity region (anLDD region), and a low concentration impurity region overlapped with thegate electrode (a GOLD region) may be provided. Thereby, a TFT 203 isformed.

Subsequently, an electrode 204 connected with either a source wiring ora drain wiring is formed. Then, an insulating film 205 having an organicmaterial or an inorganic material is formed to cover the both ends ofthe electrode 204, that is, to cover the both ends of each adjacentelectrode. Further, a protective film 206 is formed to prevent moistureor oxygen from intruding.

As above, a TFT is formed as a semiconductor element. It is obvious thata passive matrix type display device may be used even though an activematrix type display device forming a TFT in each pixel is described. Inaddition, either a top gate type TFT or a bottom gate type TFT can beused.

In addition, a semiconductor element in the peel-off layer may be a TFThaving an amorphous semiconductor film, an organic TFT, a thin filmdiode, a photoelectric conversion element having a PIN junction ofsilicon, a silicon resistor element, a sensor element (typically apressure-sensitive fingerprint sensor using polysilicon), or the like.

Afterwards, as shown in FIG. 3 (B), a light emitting layer 210 and acathode 211 are formed. As the light emitting layer, each RGB lightemitting layer may be formed or a white light emitting layer may beformed to indicate multicolor by a color conversion layer such as acolor filter. As the cathode, in the case of top emission, it may beformed with a material having light-transmitting properties, forexample, with ITO, and in the case of bottom emission, it may be formedwith a metal alloy film such as a magnesium-silver MgAg film. Inaddition, it is preferable to form continuously up to a light emittinglayer, a cathode and the like without exposing to the atmosphere.

It is preferable to perform vacuum heating to degas before or afterforming a light emitting layer containing an organic compound. Inaddition, the surface of the first electrode is preferably flat, andplanarization may be conducted by chemically or mechanically polishingtreatment (typically, a CMP technique or the like) since the lightemitting layer 210 containing an organic compound is extremely thin.

Cleaning (brush cleaning or bellclean cleaning) or plasma cleaning forcleaning a foreign substance (dust or the hie) can be performed beforeforming the light emitting layer to improve cleanliness on the surfaceof the electrode 204. The adhesive used for the transferring can beremoved clearly.

Then, peeling is performed as described below. In addition, although thecase that peeling is performed after forming a light emitting element (alight emitting layer and a cathode or an anode) is described, peelingmay be performed after forming the electrode 204. That is, apractitioner can suitably determine the peeling timing.

As shown in FIG. 3 (C), a protective film 215 is formed on the cathode215. As for the protective film, a film containing carbon or nitrogensuch as DLC, CN or SiN can be formed.

An ultraviolet (UV) protective film 216 is formed on the protective filmto protect the light emitting layer from being irradiated with anultraviolet ray. In particular, in a light emitting device of topemission, an ultraviolet protective film (an UV film) is provided toprevent a light emitting layer from deteriorating because the lightemitting layer is inevitably irradiated with an ultraviolet ray. Inother words, as an UV protective film, a film (a sheet) havingcharacteristics that transmits light from a light emitting layer, thatis, a wavelength of approximately a visible light area (400 nm to 1 μm,preferably 450 nm to 800 nm) without transmitting a wavelength of an UVarea may be used. For example, an organic resin film combined with anultraviolet absorbent, specifically, a polyester film such as polyethylene terephthalate or polyethylene-2,6-naphthalene dicarboxylate maybe used. A polyester film may be formed by a known extrusion method orthe like. In addition, an organic resin film having a structure in whicha layer absorbing an ultraviolet ray and other layers are laminated maybe used.

Then, as shown in FIG. 3 (D), a water-soluble resin 217 is formed as astress relaxation film by a spin coating method. The stress relaxationmaterial may be cured by applying heat or being irradiated with anultraviolet ray. In addition, in the case that a material cured byultraviolet ray irradiation is used, a light emitting layer can beprotected by an UV protective film when radiating an ultraviolet rayfrom above of the stress relaxation material.

Afterwards, it is preferable to separate or damage the peeling boundaryface to easily conduct peeling. Although it is not illustrated, in thepresent embodiment mode, the first substrate, the peel-off layer and thewater-soluble resin are divided by a scribe trigger which is a kind of acutter to expose a cross-section of the peeling boundary face.

Then, as shown in FIG. 3 (E), a second substrate 220 is provided overthe water-soluble resin. In the present embodiment mode, a quartzsubstrate (thickness of 1.0 to 1.5 mm) which does not have adhesivenessis used for the second substrate, and fixed using a two-sided tape 221.A two-sided tape used in the peeling process has a feature ofdeterioration in adhesiveness or self-peeling by being irradiated withan ultraviolet ray, being heated, or being soaked in liquid such aswater. In the present embodiment mode, a two-sided tape in whichadhesiveness is weakened when it is irradiated with an ultraviolet rayis used.

An adhesive such as an ultraviolet curable resin, specifically an epoxyresin system adhesive, a thermosetting resin or a resin additive may beused instead of a two-sided tape. In addition, as an auxiliarysubstrate, a quartz substrate may be fixed under the first substrateusing a two-sided tape, an adhesive or the like.

Then, as shown in FIG. 3 (F), the first substrate and the peel-off layerhaving a semiconductor element are separated by a physical means. It isillustrated to separate at the boundary between the metal oxide film andthe metal film. However, it is separated from the inside of thecrystallized metal oxide film or from the boundaries of both sides ofthe metal oxide film, in other words, it is separated at the boundarybetween the metal oxide film and the metal film, between the boundary ofthe metal oxide film and the peel-off layer, or the like. In the case itis separated inside the metal oxide film, metal oxide is sometimesdotted and adhered to the lower surface of the peel-off layer. Inaddition, in the case of separating at the boundary between the metaloxide film and the metal film, or at the boundary between the metaloxide film and the peel-off layer, the metal oxide film sometimes existsonly on the lower surface of the peel-off layer, or only on the uppersurface of the metal film. When the metal oxide is dotted or adhered tothe lower surface of the peel-off layer, metal oxide may be removed byetching or chemical or physical polishing, or remain adhered.

Then, as shown in FIG. 3 (G), the peel-off layer is fixed to a filmsubstrate 230 which is a third substrate. In the case that the filmsubstrate does not have adhesiveness, the peel-off layer is securedthrough a second adhesive 231. As for the second adhesive, anultraviolet curable resin, specifically, an adhesive such as an epoxyresin system adhesive, a thermosetting resin or a resin additive, or atwo-sided tape may be used. In the present embodiment mode, as for thesecond adhesive, water insoluble adhesive which cures by ultraviolet rayirradiation is used. In other words, as the second adhesive, a materialwhich is not peeled when the stress relaxation material is removedshould be used considering the feature of the stress relaxationmaterial. Naturally, the stress relaxation film is not necessarilyremoved.

In other words, in the present embodiment mode, adhesives in which afactor of adhesiveness deterioration of the first adhesive or peelingand a factor of curing of the second adhesive are the same are used. Forexample, when an adhesive in which adhesiveness is weakened byultraviolet ray irradiation and an adhesive which is cured byultraviolet ray irradiation are used, peeling of the second substrateand fixing to the third substrate can be done by one time of ultravioletirradiation. Therefore, process can be simplified.

Then, as shown in FIG. 3 (H), the second substrate is separated. It isseparated easily and accurately since adhesiveness of the first adhesivehas weakened.

Subsequently, as shown in FIG. 3 (I), the water-soluble resin isremoved. In the present embodiment mode, the peel-off layer fixed to thethird substrate is soaked into pure water to remove the water-solubleresin and only the water-soluble resin is removed. Afterwards, a sealingfilm 232 is formed on the UV protective film, and the peel-off layer istransferred to the third substrate. Thus, a top emission light emittingdevice is completed.

In addition, plasma cleaning or bellclean cleaning using an argon gasand an oxygen gas may be performed to remove the first and secondadhesives and the stress relaxation material precisely.

As above, a light emitting device having a TFT or the like formed overthe film substrate can be formed by a simplified peeling process. As aresult, a light emitting device which is thin, light-weight, hard todamage in being dropped, and flexible can be provided.

Plural layers to be peeled provided with a TFT or the like according toeach use of a light emitting device may be transferred to a filmsubstrate. For example, a peel-off layer having a TFT for a pixelportion and a TFT for driving a circuit is formed, then, it may betransferred to a predetermined region of a film substrate.

In addition, in the present embodiment mode, although a case of a topemission light emitting device is described, the present invention canobviously be adopted to a bottom emission light emitting device.

Embodiment Mode 2

In the present embodiment mode, a peel-off layer is in a state in whichup to a light emitting element and a liquid crystal element are formed.A case of performing peeling and transferring, that is, an example ofmanufacturing a bottom emission light emitting device by using a peelingprocess of controlling adhesiveness of an adhesive by adding anultraviolet ray and heat is described. In addition, description ofprocess or materials as in the embodiment mode 1 is omitted.

At first, to a protective film 215 are formed as the embodiment mode 1(FIG. 4 (A)). However, it is necessary to use a material havinglight-transmitting properties for a electrode 204 because it is a bottomemission light emitting device. In addition, although a stressrelaxation material may be provided, it is not particularly provided inthe present embodiment mode.

Next, as shown in FIG. 4 (B), a second substrate 220 is fixed on theprotective film 215 using a two-sided tape as an adhesive, then, thefirst substrate 200 is peeled.

Next, as shown in FIG. 4 (C), a film substrate 230 which is a thirdsubstrate is pasted by an adhesive 231 under the surface of the peel-offlayer. In the present embodiment mode, an ultraviolet ray is radiatedfrom the lower surface of the film substrate to heat because a two-sidedtape in which adhesiveness is weakened or which is peeled by heating,and an adhesive which is cured by an ultraviolet ray are used.Naturally, an ultraviolet ray may be radiated from both sides of thesubstrate. In addition, when an ultraviolet ray is transmitted throughan electrode, it may be emitted from above of the second substrate.Naturally, a two-sided tape in which adhesiveness is weakened or whichis peeled by an ultraviolet ray, and an adhesive which is cured byheating may be used. In this case, it would be appropriate to radiate anultraviolet ray from above of the second substrate.

As the present embodiment mode, by performing ultraviolet rayirradiation and heating, peeling and curing can be performed in the samestep even if a factor of adhesiveness deterioration or peeling of thetwo-sided tape 221 and a factor of curing of the adhesive are differenteach other. Thereby, a peeling process can be shortened.

Afterwards, as shown in FIG. 4 (D), the second substrate is peeled.Then, as shown in FIG. 4 (E), a sealing film 232 is formed to complete abottom emission light emitting device.

As above, it can be used as a light emitting device having a TFT or thelike formed on the film substrate by a shortened peeling process. As aresult, a light emitting device which is thin, light-weight, hard todamage in being dropped and flexible can be provided.

In addition, in the present embodiment mode, even though a bottomemission light emitting device is described, the present invention isobviously adoptable to a top emission light emitting device. In the caseof top emission, an UV protective film may be provided to prevent alight emitting layer from deteriorating.

Embodiment Mode 3

In the present embodiment mode, a peel-off layer is in a state in whichup to a semiconductor element, an electrode, an insulating film and thelike are formed, and a method for manufacturing a light emitting devicewhen peeling and transferring are performed is described.

As shown in FIG. 12 (A), a metal film 201 is formed on a first substrate200. In the present embodiment mode, a glass substrate with a thicknessof about 0.5 to 1.0 mm is utilized. As for the metal film, a monolayeror a lamination layer comprising an alloy material or a compoundmaterial of W, Ti, Ta, Mo, Nd, Ni, Co, Zr, Zn, Ru, Rh, Pd, Os and Ir orcontaining the element as its main component can be used. The metal filmmay be formed over the first substrate by sputtering using metal as atarget. Note that the film thickness of the metal film shall be 10 nm to200 nm, preferably be 50 nm to 75 nm.

When a metal alloy of the aforementioned metal (for example, an alloy ofW and Mo: W_(x)Mo_(1-x)) is used for the metal film, plural targets suchas a first metal (W) and a second metal (Mo), or a target of an alloy ofthe first metal (W) and the second metal (Mo) is disposed in a filmformation chamber; thereby the metal film may be formed by sputtering.By setting the formation of metal film appropriately as above, thepeeling process can be controlled, and a range of process is broadened.For example, when a metal alloy is used, use or disuse of heat treatmentand the temperature of heat treatment can be controlled by controllingthe composition ratio in each metal of the alloy.

Instead of the metal film, a nitrided metal film (metal nitride film)may be used. Nitrogen and oxygen may be further added to the metal film.For example, ion implantation of nitrogen or oxygen to a metal film maybe performed, or a metal film may be formed by sputtering in a filmformation chamber which shall be a nitrogen or oxygen atmosphere.Furthermore, metal nitride may be used as a target.

Afterwards, a semiconductor film is formed through a base film 207laminated on the metal film 201. In other words, an insulating filmrepresented by the base film may be provided between the metal film andthe semiconductor film in any number of layers of the insulating film.As the base film, a single layer of an insulating film having siliconsuch as an oxidation silicon film, a silicon nitride film, or a siliconoxynitride film or a lamination film thereof may be used. In the presentembodiment, SiO₂ with a thickness of 150 nm to 200 nm formed on themetal film by sputtering and SiON with a thickness of 80 to 100 nmformed on the SiO₂ by a CVD method are provided. Impurity diffusion froma substrate or a metal film to a semiconductor film can be prevented bythe base film.

In addition, an oxide film (a metal oxide film) 202 having the metal isformed on the surface of the metal film after the aforementionedprocess. The metal oxide film may be formed to have a film thickness of0.1 nm to 1 μm, preferably 0.1 nm to 100 nm, more preferably 0.1 nm to 5nm. In addition, the oxide film may be formed directly on the metalfilm.

Then, heat treatment is performed if necessary. By this heat treatment,the metal oxide film crystallizes, which causes a crystalline distortionor a lattice defect (a point defect, a line defect, a plane defect (forexample, a plane defect due to a crystallographic shear side which isformed by gathered oxygen vacancies), an expansion defect). This is astate that the metal oxide film is easily peeled.

Furthermore, by heating treatment, it is conceivable that metal oxidedifferent in crystal condition is formed by oxidation-reduction reactiondue to diffusion of hydrogen contained in the semiconductor film.Therefore, it is a state that the metal film is easily peeled.

In addition, the abovementioned heat treatment can be combined with heattreatment for crystallizing the semiconductor film. In other words, itis possible to form a crystalline semiconductor film and to crystallizea metal oxide film by heating a semiconductor film formed on a metalfilm.

After applying a metal element (represented by Ni element) whichpromotes crystallization, heat treatment may be performed or a laser maybe radiated after heat treatment to improve crystallinity of thesemiconductor film. In addition, in case that a metal element promotingcrystallization is used, it is preferable to remove the metal element bya gettering process or an etching process because it is unnecessary fora device.

Afterwards, the crystalline semiconductor film is patterned to have adesired shape, and a gate insulating film is formed using an oxidationfilm having silicon or a nitride film having silicon. A gate electrodeis formed on the crystalline semiconductor film through the gateinsulating film, and an impurity region is formed by using the gateelectrode as a mask. A lamination structure of W and TaN is used for thegate electrode, and source and drain regions, a low concentrationimpurity region (an LDD region) and a low concentration impurity regionoverlapping with the gate electrode (a GOLD region) may be provided.Thereby, a TFT 203 is formed.

Subsequently, an electrode 204 connected with either a source wiring ora drain wiring is formed. Then, an insulating film 205 having an organicmaterial or an inorganic material is formed to cover the both ends ofthe electrode 204, that is, to cover the both ends of each adjacentelectrode. As the insulating film, aside from an acrylic film (includingphotosensitive acrylic), an organic material such as polyimide,polyamide or BSB (benzocyclobutene), or aside from a silicon oxide film,an inorganic material containing silicon such as a silicon nitride film,a silicon nitride oxide film or a coated silicon oxide film (SOG: SpinOn Glass) may be used. In the present embodiment mode, photosensitiveacrylic is used. After forming the insulating film, an opening is formedby etching to expose the electrode 204. Then, a protective film 206 isformed on the insulating film since an insulating film, particularly aninsulating film having an organic material is easily intruded bymoisture, oxygen or the like which will cause deterioration of a lightemitting element. A film containing carbon or nitrogen such as DLC, CNor SiN may be formed as a protective film.

As above, a TFT is formed as a semiconductor element. It is obvious thata passive matrix type may be accepted even though an active matrix typedisplay device forming a TFT in each pixel is described.

In addition, a semiconductor element of the peel-off layer may be anorganic TFT, a thin film diode, a photoelectric conversion elementcomprising a PIN junction of silicon, a silicon resistor element, asensor element (typically a pressure-sensitive fingerprint sensor) orthe like.

Then, peeling is performed as described below. In addition, although thecase that peeling is performed after forming an electrode, an insulatingfilm and the like is described, peeling can be performed after forming alight emitting layer. That is, a practitioner can suitably determine thepeeling timing. Then, as shown in FIG. 12 (B), a water-soluble resin 210is formed as a stress relaxation material so as to cover the electrode,the insulating film and the protective film by a spin coating method.The stress relaxation material may be cured by applying heat or beingirradiated with an ultraviolet ray. In addition, in the case of using amaterial which is cured by being irradiated with an ultraviolet ray, asemiconductor element can be protected by an ultraviolet ray protectivefilm (an UV protective film) when deterioration of the semiconductorelement is concerned.

As the UV protective film, a film (or a sheet) having a feature thattransmits light from a light emitting layer that is, a wavelength of avisible light area (400 nm to 1 μm, preferably 150 nm to 800 nm) withouttransmitting a wavelength of an ultraviolet ray area (an UV region)(does not transmit at least 90% or more) may be used. For example, anorganic resin film combined with an ultraviolet absorbent, specifically,a polyester film such as poly ethylene terephthalate,polyethylene-2,6-naphthalene dicarboxylate or the like may be used. Afilm of polyester may be formed by a known extrusion method or the like.In addition, an organic resin film having a structure in which a layerabsorbing an ultraviolet ray and other layer are laminated may be used.

Afterwards, it is preferable to divide or damage the peeling boundary toconduct peeling easily. Although it is not illustrated, in the presentembodiment mode, the first substrate, the peel-off layer and thewater-soluble resin are divided by a scribe trigger which is a kind of acutter to expose a section of the peeling boundary.

Then, as shown in FIG. 12 (C), a second substrate 211 is provided on thewater-soluble resin. In the present embodiment mode, a quartz substrate(thickness 1.0 to 1.5 mm) which does not have adhesiveness is used forthe second substrate, and fixed using a two-sided tape 212. A two-sidedtape used in peeling process has features of deterioration inadhesiveness or self-peeling by being irradiated with an ultravioletray, heating or being soaked in liquid such as water. In the presentembodiment mode, a two-sided tape in which adhesiveness is weakened atthe time of being irradiated with an ultraviolet ray is used.

An adhesive such as an ultraviolet curable resin, specifically an epoxyresin system adhesive, a thermosetting resin or a resin additive may beused. In addition, the quartz substrate as an auxiliary substrate may befixed under the first substrate with a two-sided tape, an adhesive orthe like.

Then, as shown in FIG. 12 (D), the first substrate and the peel-offlayer having a first electrode and a semiconductor element are separatedby a physical means. It is illustrated to peel at the boundary betweenthe metal oxide film and the metal film. However, it is separated fromthe inside of the crystallized metal oxide film or from the boundariesof both sides of the metal oxide film, in other words, it is separatedat the boundary between the metal oxide film and the metal film, at theboundary between the metal oxide film and the peel-off layer or thelike. In the case that it is separated inside the metal oxide film,metal oxide sometimes dotted and adhered to the lower surface of thepeel-off layer. In addition, in the case of separating at the boundarybetween the metal oxide film and the metal film, or at the boundarybetween the metal oxide film and the peel-off layer, the oxide metalfilm sometimes exists only on the lower surface of the peel-off layer oronly on the upper surface of the metal film. When the metal oxide isdotted or adhered to the lower surface of the peel-off layer, metaloxide may be removed by etching, or chemical or physical polishing, orremain adhered.

Then, as shown in FIG. 12 (E), the peel-off layer is secured to a filmsubstrate 214 which is a third substrate. In the case that the filmsubstrate does not have adhesiveness, the peel-off layer is securedthrough a second adhesive 215. As for the second adhesive, anultraviolet curable resin, specifically, an adhesive such as an epoxyresin system adhesive, a thermosetting resin, a resin additive or thelike, or a two-sided tape may be used.

In the present embodiment mode, as for the second adhesive, waterinsoluble adhesive which is cured by ultraviolet ray irradiation isused. In other words, as the second adhesive, a material which is notpeeled should be used when the stress relaxation material is removedconsidering the feature of the stress relaxation material. Naturally,the stress relaxation film is not necessarily removed.

In other words, in the present embodiment mode, adhesives in which afactor of adhesiveness deterioration of the first adhesive or peelingand a factor of curing of the second adhesive are the same are used. Forexample, when an adhesive in which adhesiveness is weakened byultraviolet ray irradiation and an adhesive which is cured byultraviolet ray irradiation are used, peeling of the second substrateand fixing to the third substrate can be done by one time of ultravioletirradiation. Therefore, the process can be simplified.

Then, as shown in FIG. 12 (F), the second substrate is peeled. It ispeeled easily and accurately since adhesiveness of the first adhesivehas weakened.

Subsequently, as shown in FIG. 12 (G), the water-soluble resin isremoved. In the present embodiment mode, the peel-off layer fixed to thethird substrate is soaked into pure water to remove the water-solubleresin and only the water-soluble resin is removed.

In addition, plasma cleaning or bellclean cleaning using an argon gasand an oxygen gas may be performed to remove the first and secondadhesives and the stress relaxation material precisely.

Afterwards, as shown in FIG. 12 (H), a light emitting layer 220 and acathode 221 are formed on a protective film. At this time, an extrasupporting substrate may be prepared to reduce instability of the filmsubstrate, and the light emitting layer or the cathode may be evaporatedwith a state in which it is fixed to the supporting substrate. In thepresent embodiment mode, a light emitting layer is formed by a vacuumevaporation.

As for the light emitting layer, each RGB light emitting layer may beformed, or a white light emitting layer is formed and multicolor may beindicated by a color conversion layer such as a color filter. In thecase of top emission, a cathode may be formed of a material havinglight-transmitting properties, for example, of ITO and in the case ofbottom emission, it may be formed of a metal alloy film such as amagnesium-silver MgAg film.

Before or after forming a light emitting layer containing an organiccompound, it is preferable to perform vacuum heating to degas. Inaddition, because the light emitting layer 210 containing an organiccompound is extremely thin, it is preferable that the surface of thefirst electrode is flat. It may be planarized by treatment polishingchemically or mechanically (typically by a CMP technology or the like).

Cleaning (brush cleaning or bellclean cleaning) or plasma cleaning toclean a foreign substance (dust or the like) can be performed beforeforming the light emitting layer to improve cleanliness on the surfaceof the electrode 204. The adhesive used for the transferring can be alsoremoved completely.

Then, as shown in FIG. 12 (I), a protective film 222 is formed on thecathode and a sealing film 223 is formed. In addition, when space isformed between the sealing film and the cathode, nitrogen purge may beperformed then a desiccating agent or the like may be sealed to preventdeterioration of a light emitting layer or the like. In addition, it ispreferable to sequentially form to the light emitting layer, the cathodeand the protective film without exposing to atmosphere.

Thus, the peel-off layer is transferred to the film substrate tocomplete a top emission light emitting device. As a result, a lightemitting device which is thin, light-weight, hard to damage in beingdropped and flexible can be provided.

In addition, plural layers to be peeled provided with a TFT or the hieaccording to each use of a light emitting device may be transferred. Forexample, a peel-off layer having a TFT for a pixel portion and a TFT fordriving circuit is formed, then, it may be transferred to apredetermined region of the film substrate.

In addition, in the present embodiment mode, although the case of a topemission light emitting device is described, the present invention isobviously adoptable to a bottom emission light emitting device.

Embodiment Mode 4

In the present embodiment mode, a peel-off layer is in a state in whichup to a semiconductor element, an electrode, an insulating film and thelike are formed, and a case of performing peeling and transferring, andan example of manufacturing a bottom emission light emitting device byusing a peeling process of controlling adhesiveness of an adhesive byadding an ultraviolet ray and heat are described. In addition,description of the process or materials as in the embodiment mode isomitted.

At first, up to a protective film 206 are formed as the embodiment mode1 (FIG. 13 (A)). However, it is necessary to use a material havinglight-transmitting properties for an electrode 204 since it is a bottomemission light emitting device. In addition, although a stressrelaxation material may be provided, it is not particularly provided inthe present embodiment mode.

Next, as shown in FIG. 13 (B), a second substrate 211 is fixed on theprotective film 206 using a two-sided tape 212 as an adhesive, then, afirst substrate 200 is peeled.

Then, as shown in FIG. 13 (C), a film substrate 214 which is a thirdsubstrate is pasted under the surface of the peel-off layer by anadhesive 215. In the present embodiment mode, an ultraviolet ray isradiated from the lower surface of the film substrate to heat because atwo-sided tape in which adhesiveness is weakened or which is peeled byheating, and an adhesive which is cured by an ultraviolet ray are used.Naturally, an ultraviolet ray may be radiated from both sides of thesubstrate. In addition, when an ultraviolet ray transmits through anelectrode, it may be radiated form above of the second substrate.Naturally, a two-sided tape in which adhesiveness is weakened or whichis peeled by an ultraviolet ray, and an adhesive which is cured byheating may be used. In this case, it would be appropriate to radiate anultraviolet ray from above of the second substrate.

As the present embodiment mode, peeling and curing can be performed inthe same or step by performing ultraviolet ray irradiation and heatingeven if a factor of adhesiveness deterioration or peeling of thetwo-sided tape 221 and a factor of curing of the adhesive are differentfrom each other. Thereby, a peeling process can be simplified.

Afterwards, as shown in FIG. 13 (D), the second substrate is peeled.Then, as shown in FIG. 13 (E), a light emitting layer 220 and a cathode211 are formed. Then, a protective film 222 is formed on the cathode anda sealing film 223 is provided to complete a bottom emission lightemitting device.

As above, it can be used as a light emitting device having a TFT or thelike formed on the film substrate by a shortened peeling process. As aresult, a light emitting device which is thin, light-weight, hard todamage in being dropped and flexible can be provided.

In addition, in the present embodiment mode, even though a bottomemission light emitting device is described, the present invention isobviously adoptable to top emission light emitting device. An UVprotective film may be provided when deterioration of a semiconductorelement is concerned by ultraviolet ray irradiation.

Embodiment Mode 5

In the present embodiment mode, a peel-off layer is in a state in whichup to a light emitting element and a liquid crystal element are formed,and a case of performing peeling and transferring, and a case ofmanufacturing a liquid crystal display device by using a peeling processof controlling adhesiveness of an adhesive by heating are described.

As shown in FIG. 5 (A), a metal film 301 is formed on a fast substrate300. As for the first substrate and the metal film, material describedin the embodiment mode 1 may be used. In the present embodiment mode, analloy film of Mo and W is formed on a glass substrate. At this time,plural targets such as a first metal (W) and a second metal (Mo), or atarget of an alloy of the first metal (W) and the second metal (Mo) isdisposed in a film formation chamber, thereby the metal film may beformed by sputtering. By setting the composition of metal filmappropriately as above, the peeling process can be controlled, and arange of process is broadened.

Afterwards, a TFT 303 is formed through base films 307 as the embodimentmode 1, and an electrode 304 connected to one of wirings of the TFT isformed.

In addition, by the time the semiconductor film or the base film isformed, a metal oxide film 302 which is an oxide containing the metal isformed on the metal film. Then a counter substrate 305 provided with acolor filter or the like is arranged to form a liquid crystal 306between the first substrate and the counter substrate. A film substratemay be used as the counter substrate. The liquid crystal may be injectedby a vacuum injection method or by dropping in the vacuum atmosphere. Asa liquid crystal material, a known material, for example, a dispersedliquid crystal, a ferroelectric liquid crystal, an antiferroelectricliquid crystal, or the like may be used. As for a liquid crystal withhigh viscosity such as a dispersed liquid crystal, it would beappropriate to use a dropping method.

In addition, when manufacturing a liquid crystal display device,although a spacer is formed or sprayed to keep the flexible substratesapart, three times spacer than usual may be formed or sprayed. Inaddition, a spacer may be manufactured softer than the case of beingused to a usual glass substrate. Moreover, a spacer need to be fixed notso as to move since the film substrate is flexible.

Furthermore, when a film substrate used as a counter substrate or athird substrate transmits moisture or impurity, it may be covered withan organic material such as polyvinyl alcohol, ethylene-vinylalcoholcopolymer, or an inorganic material such as polysilazane, aluminumoxide, silicon oxide silicon nitride, or a barrier film formed oflamination of these.

Afterwards, as shown in FIG. 5 (B), a water-soluble resin 310 is formedas a stress relaxation material by spin coating.

Next, as shown in FIG. 5 (C), a second substrate 311 is fixed on thewater-soluble resin by a two-sided tape 312. Then, the first substrateis separated by a physical means such as a tape. At this time, it isseparated from the inside the crystallized metal oxide film or from theboundaries of both sides of the metal oxide film, in other words, it isseparated at the boundary between the metal oxide film and the metalfilm or at the boundary between the metal oxide film and the peel-offlayer. In the case that it is separated inside the metal oxide film,metal oxide sometimes dotted and adhered to the lower surface of thepeel-off layer. In this case, metal oxide may be removed by etching orpolishing or adhered.

Then, as shown in FIG. 5 (D), a film substrate 315 corresponding to athird substrate is pasted. In the present embodiment mode, an adhesive316 which is cured by heating is used to fix the film substrate. At thistime, curing of the adhesive and peeling of the two-sided tape can beperformed at the same time by the present process because the two-sidedtape 312 in which adhesiveness is weakened or which is peeled by itselfby heating is used. As a result, a manufacturing process can beshortened.

The abovementioned process may also be performed by radiating anultraviolet ray. In that case, a two-sided tape which is peeled byultraviolet ray irradiation and an adhesive which is cured byultraviolet ray irradiation may be used.

Then, as shown in FIG. 5 (E), the second substrate is peeled. It can bepeeled easily and uniformly since adhesiveness has weakened.

Then, as shown in FIG. 5 (F), the water-soluble resin is removed bysoaking it in purified water. Afterwards, a liquid crystal displaydevice having a TFT formed on the film substrate is completed byproviding a polarizing plate or the like suitably.

As above, a liquid crystal display device having a TFT or the likeformed on a film substrate can be formed by the simplified manufacturingprocess. As a result, a liquid crystal display device which is thin,light-weight, hard to damage in being dropped and flexible can beprovided.

Embodiment Mode 6

In the present embodiment mode, a peel-off layer is in a state in whichup to a light emitting element and a liquid crystal element are formed,and a case of performing peeling and transferring, and an example ofmanufacturing a liquid crystal display device by using a peeling processof controlling adhesiveness by radiating an ultraviolet ray in additionto heating are described. In addition, description of the same processor materials as in the embodiment mode 5 is omitted.

At first, a metal film 301, a metal oxide film 302, a base film 307, aTFT 303, an electrode 304, a counter substrate 305 and a liquid crystal306 are formed over a first substrate 300 as in the embodiment mode 3.(FIG. 6 (A)).

Then, as shown in FIG. 6 (B), a second substrate 311 is pasted on thecounter substrate by a two-sided tape 311. Afterwards, the firstsubstrate is peeled by a physical means. In addition, although a stressrelaxation material may be provided, it is not particularly provided inthe present embodiment mode.

Next, as shown in FIG. 6 (C), a film substrate 315 is pasted as a thirdsubstrate by an adhesive 316. In the present embodiment mode, theadhesive is cured by being irradiated with an ultraviolet ray from bothsides of the substrate while heating the entire substrate. At the sametime, adhesiveness of the two-sided tape 312 had weakened or peeled byitself by heating or ultraviolet ray irradiation. That is, a feature isthat the two-sided tape to fix the second substrate is peeled and theadhesive for fixing the film substrate is cured by this step. Moreover,the two-sided tape may be either one which is peeled by heating or theother one which is peeled by ultraviolet ray irradiation since theheating and the ultraviolet ray irradiation are performedsimultaneously. Thereby, a manufacturing margin can be widened.

Afterwards, as shown in FIG. 6 (D), a liquid crystal display device iscompleted by peeling the second substrate. As above, a liquid crystaldisplay device having a TFT or the like formed on the film substrate canbe formed by the simplified manufacturing process. As a result, a liquidcrystal display device which is thin, light-weight, hard to damage inbeing dropped and flexible can be provided.

Embodiment Mode 7

In the present embodiment mode, a peeling layer is in a state in whichup to a light emitting element and a liquid crystal element are formed,and a case of performing peeling and transferring, and a case forming aliquid crystal display device by using a peeling process of controllingadhesiveness of an adhesive by heating are described.

As shown in FIG. 14 (A), a metal film 301 is formed on a first substrate300. As for the first substrate or the metal film, a material describedin the Embodiment Mode 1 may be used. In the present embodiment mode, analloy film of Mo and W is formed on a glass substrate. At this time,plural targets such as a first metal (W) and a second metal (Mo), or atarget of an alloy of the first metal (W) and the second metal (Mo) isdisposed in a film formation chamber, thereby the metal film may beformed by sputtering. By setting composition of a metal filmappropriately like this, the peeling process can be controlled, and aprocess margin is widened. Afterwards, a TFT 303 is formed as in theEmbodiment Mode 1, and an electrode 304 connected to one of wirings ofthe TFT is formed.In addition, after a semiconductor film or a base film 307 are formed, ametal oxide film 302 which is an oxide of the metal is formed on themetal film.Then, as shown in FIG. 14 (B), a water-soluble resin 310 is formed as astress relaxation material by a spin coating method.

Next, as shown in FIG. 14 (C), a second substrate 311 is fixed on thewater-soluble resin by using a two-sided tape 312 as an adhesive.Afterwards, the first substrate is peeled by a physical means. At thistime, it is separated from the inside the crystallized metal oxide filmor from the boundaries of both sides of the metal oxide film, in otherwords, it is separated at the boundary between the metal oxide film andthe metal film, at the boundary between the metal oxide film and thepeel-off layer. In the case it is separated inside the metal oxide film,metal oxide sometimes dotted and adhered to the lower surface of thepeel-off layer. In this case, the metal oxide may be removed by etchingor polishing or remain adhered.

Then, as shown in FIG. 14 (D), a film substrate 315 corresponding to athird substrate is pasted. In the present embodiment mode, an adhesive316 which is cured by heating is used to fix the film substrate. At thistime, curing of the adhesive and peeling of the two-sided tape can beperformed at the same time by the present process because the two-sidedtape 312 in which adhesiveness is weakened or which is peeled by itselfby heating is used. As a result, a manufacturing process can besimplified.

The abovementioned process may also be performed by radiating anultraviolet ray. In that case, a two-sided tape which is peeled by beingirradiated with an ultraviolet ray and an adhesive which is cured bybeing irradiated with an ultraviolet ray may be used.

Then, as shown in FIG. 14 (E), the second substrate is peeled. It can bepeeled easily and uniformly since adhesiveness of the two-sided tape hasweakened. Then, as shown in FIG. 14 (F), the water-soluble resin isremoved by soaking it in purified water.

Then, as shown in FIG. 14 (G), a counter substrate 305 provided with acolor filter or the like is arranged to form a liquid crystal 306between the first substrate and the counter substrate. In addition,although it is not illustrated, a polarizing plate is providedappropriately. A film substrate may be used as the counter substrate.The liquid crystal may be injected by a vacuum injection method or bydropping in the vacuum atmosphere. As a liquid crystal material, a knownmaterial, for example, a dispersed liquid crystal, a ferroelectricliquid crystal, an antiferroelectric liquid crystal or the like may beused. As for a liquid crystal with high viscosity to some extent like adispersed liquid crystal, it would be appropriate to use a droppingmethod.

In addition, when manufacturing a liquid crystal display device,although a spacer is formed or sprayed to keep the substrates apart,about three times spacer than usual may be formed or sprayed to keep theinterval of flexible substrate apart. In addition, a spacer may bemanufactured to be softer than in the case of being used for a usualglass substrate. Moreover, a spacer need to be fixed not so as to movesince the film substrate is flexible.

Furthermore, when a film substrate used as a counter substrate or athird substrate transmits moisture or an impurity, it may be coveredwith an organic material such as polyvinyl alcohol,ethylene-vinylalcohol copolymer or the like or an inorganic materialsuch as polysilazane, aluminum oxide, silicon oxide, silicon nitride orthe like or a barrier film formed of lamination of these.

As above, a light emitting device having a TFT or the like formed on thefilm substrate can be manufactured by a simplified peeling process. As aresult, a light emitting device which is thin, light-weight, hard todamage in being dropped and flexible can be provided.

Embodiment Mode 8

In this present embodiment mode, a peel-off layer is in a state in whichup to a light emitting element and a liquid crystal element are formed,and an example of manufacturing a liquid crystal display device whenusing a peeling process of controlling adhesiveness by radiating anultraviolet ray in addition to heating is described. In addition,description of the same process or materials as in the embodiment mode 7is omitted.

At first, a metal film 301, a metal oxide film 302, a base film 307, aTFT 303 and an electrode 304 are formed over a first substrate 300 as inthe embodiment mode 3 (FIG. 15 (A)). Then as shown in FIG. 15 (B), asecond substrate 311 is pasted on the electrode by a two-sided tape 312as an adhesive. Afterwards, the first substrate is peeled by a physicalmeans. In addition, although a stress relaxation material may beprovided, it is not particularly provided in the present embodimentmode.

Next, as shown in FIG. 15 (C), a film substrate 315 is pasted by anadhesive 316 as a third substrate. In the present embodiment mode,ultraviolet rays are radiated from both sides to cure the adhesive whileheating the entire substrate. At the same time, adhesiveness of thetwo-sided tape 312 is weakened or peeled by itself by heating orultraviolet ray irradiation.

That is, a feature is that the two-sided tape for fixing the secondsubstrate is peeled and the adhesive for fixing the film substrate iscured according to the present process. Moreover, the two-sided may beeither one which is peeled by heating or the other one which is peeledby ultraviolet ray irradiation since the heating and the ultraviolet rayirradiation are performed simultaneously. Thereby, a manufacturingmargin can be widened.

Afterwards, as shown in FIG. 15 (D), the second substrate is peeled by aphysical means. Then, as shown in FIG. 15 (E), a counter substrate 320provided with a color filter or the like is formed to form a liquidcrystal 321.

As above, a liquid crystal display device having a TFT and the likeformed on the film substrate can be manufactured by the simplifiedmanufacturing process. As a result, a liquid crystal display devicewhich is thin, light-weight, hard to damage in being dropped andflexible can be provided.

Embodiment Mode 9

In this present embodiment mode, a method of gang printing to form adisplay device having plural semiconductor elements from a large-sizesubstrate (for example, 600×720 mm substrate) is described.

FIG. 7 (A) shows a state in which plural display devices orsemiconductor element groups 501 are formed through an insulating film510 of a base film or the like on the first substrate 500. The displaydevice includes a light emitting device, a liquid crystal display deviceand other types of display devices, and moreover, it may be anelectronics device having a semiconductor element formed by the peelingprocess of the present invention.Semiconductor element groups constitute a display portion, a drivingcircuit portion or the like and are formed according to the peelingprocess of the present invention.

Mass production efficiency is improved by using a large-size substrateas the first substrate and by manufacturing plural display devices orsemiconductor elements. However, it is preferable to use a device havinga pressure reduction function (a pressure reduction device) as shown inFIG. 7 (B) since there is a possibility that it becomes difficult topeel the first substrate or the second substrate uniformly. FIG. 7 (B)shows a cross-sectional view taken along the line a-a′ and a step forpeel the second substrate. In other words, a metal film 502, a displaydevice or semiconductor element groups 501 formed through a metal oxidefilm 503 and a second substrate 505 formed on the display device or thesemiconductor element groups are provided over the first substrate 500.Preferably, a stress relaxation material 504 may be provided so as tocover the display device or the semiconductor element groups. Then apressure reduction device 508 having vacancies 506 connected with a pump507 is fixed. An auxiliary substrate or the like may be arranged betweenthe first substrate and the pressure reduction device. Moreover, it ispreferable to arrange a pressure reduction device also on the secondsubstrate side and to fix it. Then, the state inside the vacanciesbecome pressure reduced or vacuumed. Therefore, the first substrate canbe peeled uniformly because the first substrate or the second substratecan be absorbed with constant suction power. In addition, thecross-section of the peeled plane may be exposed and the cross-sectionmay be damaged with a cutter or the like. Afterwards, even thoughtransferring to a third substrate is performed, it may be carried out ina state in which the second substrate is being absorbed. In that case,peeling or curing the adhesive is performed by radiating an ultravioletray or heating with the third substrate is being fixed to the pressurereduction device to transfer the absorbed second substrate. At thistime, the pressure reduction device may be formed of a material whichtransmits an ultraviolet ray. It is sometimes difficult to fix the filmsubstrate corresponding to the third substrate uniformly since it isflexible. However, transferring, peeling and even manufacturing of adisplay device can be performed precisely and simply by fixing uniformlywith a pressure reduction device or the like.

The present embodiment mode can be combined with any of Embodiment Modes1 through 4.

Embodiment Mode 10

The present invention can be adopted to display portions of varioustypes of electronics devices. As electronics devices, portableinformation terminals (such as cellular phones; mobile computers; sheetcomputers; wearable computers; portable video game players andelectronic notebooks), video cameras, digital cameras, goggle typedisplays, displays, navigation systems and the like are given asexamples. An operative example of the electronic devices is shown inFIG. 8.

FIG. 8 (A) illustrates a mobile computer which includes a main body4101, a stylus 4102, a display portion 4103, operation buttons 4104, anexternal interface 4105 and the like. The display device of the presentinvention is used for the display portion 4103. A mobile computer whichis light-weight, thin and hard to damage in being dropped can beprovided according to the present invention. Moreover, a display portionmay have a curved surface since the display device of the presentinvention is sufficient flexibility.

FIG. 8 (B) illustrates an electronic book reader which includes adisplay portion 4201 and the like. The display device of the presentinvention is used for a display portion 4202. An electronic book readerwhich is light-weigh, thin and hard to damage in being dropped can beprovided according to the present invention. Moreover, the displaydevice of the present invention can be used as a display portion of atwo-page spread electronic book, an electronic roll-up book or the likesince it has sufficient flexibility.

FIG. 8 (C) illustrates an IC card which includes a main body 4301, adisplay portion 4302, an integrated circuit portion 4303 and the like.The display device of the present invention is used for the displayportion 4302. It becomes possible to provide a display portion on anextremely thin IC card according to the present invention. In addition,a semiconductor element of the integrated circuit portion may bemanufactured by using the peeling method of the present invention.

FIG. 8 (D) illustrates a sheet-type cellular phone which includes a mainbody 4401, a display portion 4403, a voice input portion 4404, a voiceoutput portion 4405, a switch 4406, an external connection port 4407 andthe like. It can be connected with earphones 4408 that is preparedseparately through the external connection port 4407. A display deviceformed according to the present invention is used for the displayportion 4403 which is a touch panel type provided with a sensor.Therefore, a series of operations can be performed by touching atouch-panel type operation keys 4409 displayed on the display portion4403. In addition, a thin film circuit formed by the present inventionmay be used as a various signal processing circuit provided inside themain body 4401. A cellular phone which is light-weight, thin and hard todamage in being dropped can be provided according to the presentinvention.

FIG. 8 (E) illustrates a robot which includes an arm portion 4501, atrunk portion 4502, a head portion 4503, a display portion 4504 and thelike. The display device of the present invention is used for thedisplay portion 4504. FIG. 8 (F) is an advertising pillar 4602 providedwith a display portion 4601. The present invention is used for thedisplay portion 4601. Moreover, the display portion of the presentinvention may be fixed on a window of a car or the like. In this way,the display device of the present invention has an effect that it can beused with being secured to a round substrate, since it has a feature offlexibility.

As above, the present invention is applicable to extremely wide rangeand can be utilized to electronics devices in all fields. In particular,the present invention that realizes thin or light-weight is extremelyefficient to electronics devices of FIG. 8 (A) through (F).

Embodiment Mode 11

A panel mounted with a pixel portion, a driver circuit for controllingthe pixel portion, a memory circuit, and a CPU comprising a control unitand an arithmetic unit over the same insulating surface will beexplained in this present embodiment. In other words, a driving circuit,a logical circuit or the like can be formed in addition to the displayportion according to the peeling process of the present invention.

FIG. 9 shows the appearance of a panel. The panel has a pixel portion3000 where plural pixels are arranged in matrix over a substrate 3009. Ascanning line driver circuit 3001 and a signal line driver circuit 3002for controlling the pixel portion 3000 are provided at the periphery ofthe pixel portion 3000. In the pixel portion 3000, an image is displayedaccording to a signal supplied from the driver circuit.

The counter substrate may be provided only over the pixel portion 3000and the driver circuits 3001 and 3002, or may be provided over theentire surface. Note that it is preferable that a CPU 3008 that maygenerate heat to be provided to be in contact with a heat sink.

Further, the panel also has a VRAM 3003 (video random access memory,display only memory) for controlling the driver circuits 3001 and 3002,and decoders 3004 and 3005 for controlling the VRAM 3003 at theperiphery of the VRAM 3000. In addition, the panel has a RAM 3006, adecoder 3007 for controlling the RAM 3006 and the CPU 3008 at theperiphery of the RAM 3006.

All elements constituting a circuit over the substrate 3009 are formedof a polycrystalline semiconductor (polysilicon) that has higherfield-effect mobility and higher ON current than that of an amorphoussemiconductor. Therefore, plural circuits can be formed into anintegrated circuit over one insulating surface. A pixel portion 3001,driver circuits 3001 and 3002 and other circuits are formed over asupporting substrate first, and then peeled by the peeling methodaccording to the present invention, then, pasted with each other therebyachieving an integrated structure over the flexible substrate 3009.Although the structure of the plural pixels arranged in the pixelportion is not limited, arrangement of VRAM 3003 and RAM 3006 may beomitted by providing SRAM for each of the plural pixels.

EMBODIMENT Embodiment 1

In the present embodiment, the result of observation of an oxide layerwith a TEM on the substrate and the semiconductor side after peeling isshown.

A W film with a thickness of 50 nm by sputtering, a silicon oxide filmwith 200 nm by sputtering, a silicon oxynitride film with 100 nm thickas an insulating film by a plasma CVD method and an amorphous siliconfilm with 50 nm thick as a semiconductor film by a plasma CVD method aresequentially laminated.

Afterwards, it is peeled by a physical means such as apolytetrafluoroethylene tape after conducting heat treatment for 1 hourat 500 degrees and for 4 hours at 550 degrees. FIG. 10 shows a TEMphotograph of the W film and the oxide layer on the substrate side. FIG.11 shows a TEM photograph of the oxide layer and the silicon oxide filmon the semiconductor film side.

In FIG. 10, a metal oxide film remains unevenly in contact with themetal film. Likewise, also in FIG. 11, a metal oxide film remainsunevenly in contact with the silicon oxide film. It is demonstrated fromthe both TEM photographs that peeling is conducted inside of the layerof the metal oxide film and its both boundaries. In addition, it isunderstood that the metal oxide film is adhered to the metal film andthe silicon oxide film and remains unevenly. Next, the peeled surfacesof the substrate side and the semiconductor film side after peeling aremeasured with XPS. Waveform separation is performed on the resultantspectrum. The obtained detection element and quantitative result are asfollows.

On the semiconductor film side after peeling, W1 (tungsten W) and W2(tungsten oxide Wo_(x), X is almost 2) remains 0%; W3 (tungsten oxideWo_(x), 2<X<3) 16%; and W4 (tungsten oxide WO₃ or the like) 84%, on thecontrary, on the substrate side where W1 remains 44%; W2, 5%; W3, 10%and W4, 42%.

Therefore, when peeling is conducted at the boundary between the metaloxide film and the metal film, at the boundary between the metal oxidefilm and the silicon oxide film, or inside the metal oxide film, it isunderstood that W1 and W2 remains all on the substrate side, two-thirdsof W4 remains on the semiconductor film side and one-third remains onthe substrate side. In other words, peeling easily occurs inside themetal oxide film, particularly from the boundary of W3 or W4.In addition, in the present experiment, there is no W2 on thesemiconductor film side and W2 is adhered to the substrate side.However, a case in which W2 is adhered to the semiconductor film sideand there is no W2 on the substrate side can be conceivable conversely.That is, it is conceivable that a metal oxide film is dotted between afilm substrate and a single base film or a laminated base film providedunder a semiconductor film when a display device or the like accordingto the present invention is manufactured, and it is transferred to thefilm substrate with a state in which the metal oxide film is adhered alittle on the semiconductor film side.

What is claimed is:
 1. A method for manufacturing a display devicecomprising the steps of: forming a metal film over a substrate; forming,on and in contact with the metal film, an oxide of a metal comprised inthe metal film; forming, over the oxide of the metal, a peel-off layercomprising: an insulating film; a thin film transistor over theinsulating film; a light emitting element in electrical contact with thethin film transistor, the light emitting element comprising a lightemitting layer containing an organic compound sandwiched between twoelectrodes; and separating the peel-off layer from the substrate.
 2. Themethod for manufacturing a display device according to claim 1, furthercomprising the step of: fixing, in place of the substrate, a filmsubstrate to the peel-off layer by using an adhesive.
 3. The method formanufacturing a display device according to claim 1, wherein separatingthe peel-off layer from the substrate occurs at a boundary between theoxide of the metal and the metal film, or at the boundary between theoxide of the metal and the peel-off layer.
 4. The method formanufacturing a display device according to claim 1, wherein separatingthe peel-off layer from the substrate occurs inside the oxide of themetal.
 5. The method for manufacturing a display device according toclaim 1, further comprising the step of: exposing a cross-section of aboundary face of the peel-off layer prior to separating the peel-offlayer from the substrate.
 6. The method for manufacturing a displaydevice according to claim 1, further comprising the step of: addingoxygen to the metal film prior to forming the peel-off layer.
 7. Themethod for manufacturing a display device according to claim 1, whereinthe display device is a bottom emission flexible light emitting device.8. An electronic device comprising the display device manufacturedaccording to claim
 1. 9. A method for manufacturing a display devicecomprising the steps of: forming a tungsten film over a substrate;forming a tungsten oxide on and in contact with the tungsten film;forming, over the tungsten oxide, a peel-off layer comprising: aninsulating film comprising silicon, nitrogen and oxygen; a thin filmtransistor over the insulating film; a light emitting element inelectrical contact with the thin film transistor, the light emittingelement comprising a light emitting layer containing an organic compoundsandwiched between two electrodes; and separating the peel-off layerfrom the substrate.
 10. The method for manufacturing a display deviceaccording to claim 9, further comprising the step of: fixing, in placeof the substrate, a film substrate to the peel-off layer by using anadhesive.
 11. The method for manufacturing a display device according toclaim 9, wherein separating the peel-off layer from the substrate occursat a boundary between the tungsten oxide and the tungsten film, or atthe boundary between the tungsten oxide and the peel-off layer.
 12. Themethod for manufacturing a display device according to claim 9, whereinseparating the peel-off layer from the substrate occurs inside thetungsten oxide.
 13. The method for manufacturing a display deviceaccording to claim 9, further comprising the step of: exposing across-section of a boundary face of the peel-off layer prior toseparating the peel-off layer from the substrate.
 14. The method formanufacturing a display device according to claim 9, further comprisingthe step of: adding oxygen to the tungsten film prior to forming thepeel-off layer.
 15. The method for manufacturing a display deviceaccording to claim 9, wherein the display device is a bottom emissionflexible light emitting device.
 16. An electronic device comprising thedisplay device manufactured according to claim
 9. 17. A method formanufacturing a display device comprising the steps of: forming a metalfilm over a first substrate; forming, on and in contact with the metalfilm, an oxide of a metal comprised in the metal film; forming, over theoxide of the metal, a peel-off layer comprising: an insulating film; athin film transistor over the insulating film; a light emitting elementin electrical contact with the thin film transistor, the light emittingelement comprising a light emitting layer containing an organic compoundsandwiched between two electrodes; fixing, over the peel-off layer, asecond substrate to the peel-off layer by using a first adhesive;separating the peel-off layer from the first substrate; fixing, in placeof the first substrate, a film substrate to the peel-off layer by usinga second adhesive; separating the second substrate from the peel-offlayer.
 18. The method for manufacturing a display device according toclaim 17, further comprising the step of forming over the peel-off layera film in place of the second substrate after the separating of thesecond substrate from the peel-off layer.
 19. The method formanufacturing a display device according to claim 17, wherein separatingthe peel-off layer from the first substrate occurs at a boundary betweenthe oxide of the metal and the metal film, or at the boundary betweenthe oxide of the metal and the peel-off layer.
 20. The method formanufacturing a display device according to claim 17, wherein separatingthe peel-off layer from the first substrate occurs inside the oxide ofthe metal.
 21. The method for manufacturing a display device accordingto claim 17, further comprising the step of: exposing a cross-section ofa boundary face of the peel-off layer prior to separating the peel-offlayer from the first substrate.
 22. The method for manufacturing adisplay device according to claim 17, further comprising the step of:adding oxygen to the metal film prior to forming the peel-off layer. 23.The method for manufacturing a display device according to claim 17,wherein the display device is a bottom emission flexible light emittingdevice.
 24. An electronic device comprising the display devicemanufactured according to claim 7.